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83 In the studies, pedestrians who were blind repeatedly Implications of Field Study Results crossed the street at roundabouts and CTLs. The participants were at all times accompanied by a certified O&M special- There are many challenges inherent in translating accessi- ist who was trained to prevent collisions by intervening in bility research into policy guidance. Roundabouts and CTLs, along with the individuals who use them, are diverse. The the crossing attempt in the event that participants misjudged facilities differ in terms of vehicle volume, level of ambient traffic patterns. The data these studies yielded were very com- noise, driver culture, and physical design. The individuals plex. A multitude of factors were observed and recorded both who participated in the NCHRP Project 3-78A studies dif- in the field in real-time and in post-processing from video fered in their propensity for risk taking, hearing ability, travel recordings. Details on the study methodology are given in experience, and physical and cognitive abilities. It was a chal- Chapter 3. The data analysis involved formulation of a new lenge in this project to draw appropriate, general conclusions analysis framework for quantitatively describing pedestrian from the results from a program of research that was limited accessibility that is described in Chapter 4. Detailed results are in comparison to the range of factors that might influence presented in Chapter 5 with supplemental results given in street crossing. The program was limited by resources and Appendix A. by the availability of adequate numbers of participants near Third, the research presented two approaches for exten- roundabout and CTL facilities. Because of these factors, the sion of the analysis framework and the field study results to team narrowed the focus by studying relatively skilled, func- other locations and traffic patterns (Chapter 6). Using the tionally blind individuals and by evaluating only two treat- pedestrian and driver behavioral attributes defined in the ments at roundabouts (PHB and raised crosswalk) and two at analysis framework, the team developed regression-based CTLs (sound strips and flashing beacon). Other limitations mixed-priority models to predict pedestrian delay at unsignal- in the work included the fact that sample sizes were modest ized crosswalks. The term "mixed-priority" refers to a cross- and participants were recruited rather than selected randomly ing situation where some pedestrians cross in gaps between from a population. moving vehicles while others cross in front of yielding vehicles. Despite the limitations noted above, the team derived con- The models are sensitive to the fact that there is variability clusions from the studies where possible. Given that there are in the rates of occurrence of gaps and yields as well as in the numerous explanations for the results obtained, the team also rates of utilizing these opportunities. Separate delay mod- hypothesized about the possible explanations or interpreta- els were developed for each of the three facility types, and tions of the findings. The information that follows is organ- guidance was provided on how the models may be applied ized by type of facility (CTL, single-lane roundabout, and to other sites. The extension piece further provided guid- two-lane roundabout). ance for how microsimulation models can be used to analyze In regard to the CTL, the studies showed high rates of inter- pedestrianvehicle interaction at roundabouts and channel- vention at pretest for both CTLs (9.4% and 5.6%, respec- ized turn lanes. The discussion demonstrated that the analy- tively). Since the pretests at the two locations were completed sis framework is compatible with a simulation environment. by the same participants on the same day, and no treatment Special attention was given to a sensitivity analysis of different was in place, it is likely that the differences observed in the pedestrian signalization options at single-lane and two-lane two locations in regard to intervention rate are due to ambi- roundabouts. ent noise levels or vehicle speeds and volumes. Traffic counts Modeling was not done with regard to the safety of pedes- were higher at the SS-ONLY installation, which was the CTL trians who are blind. The direct measure of safety used in this with the higher intervention rate. Regardless of the cause, research (O&M interventions) was not frequent enough to sup- intervention rates at both CTL locations were very high and port modeling. Nonetheless, interventions were numerous, represent an unacceptable level of risk for the participants. representing times where there was a high likelihood of the The pretest at the two CTLs further showed high average blind pedestrian being injured or killed without evasive action delay per subject at 26.2 s and 23.4 s, respectively, to cross a on the part of a driver or the pedestrian. In the worst test con- single lane of traffic. However, individual delays were much dition (CTL pretest), the probability of intervention was 1 in 18. higher, and some trials even timed out after participants were Viewing this statistic from the perspective of a blind traveler not able to cross within 2 min. who commuted across that CTL, this level of risk is unaccept- The posttest data revealed that both tested treatments yielded able. Intervention rates were also high at other sites, including a significant reduction in intervention rates and reduced aver- the two-lane roundabout at pretest and one of the single-lane age delay to some extent. The combination of sound strips and roundabouts. Consequently, the delay modeling effort should flashing beacons reduced the intervention rate and delay only be interpreted as one piece of guidance in the broader more than the sound strips alone, although the difference question of accessibility of a site. between the two posttest intervention rates is not statistically

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84 significant (p = 0.3483). However, the team concluded that ing traffic conditions, but some risk remains. Similar to the even the lower intervention rate (1.4%) was still unacceptably Golden site, it is unclear if and how behavior and performance high and that additional treatments are needed at this CTL to measures would change under different traffic conditions. achieve an acceptable level of crossing safety. The Raleigh single-lane roundabout data was collected as The research team did not evaluate any treatments at part of an earlier research effort, and the data was reanalyzed single-lane roundabouts. This research conducted pretests at using the analysis framework developed as part of this project. a single-lane roundabout in Charlotte, NC, and Golden, CO. The intervention rate was the highest of all roundabouts stud- Also included in this report are findings from a study con- ied (although the rate was lower than the rate at the CTL site ducted at a single-lane roundabout in Raleigh, NC. The team studied). The team considers the 3.9% intervention rate at did not pursue treatment installation as originally planned at this intersection to be unacceptable and suggests that a treat- the Charlotte single-lane roundabout, partly because it was ment is needed at this intersection to reduce crossing risk. It believed that the treatment would be unlikely to result in a needs to be noted that this prior study actually included some measurable effect of pedestrian safety, based on an intervention participants with normal vision and that these sighted partic- assessment. The pretest intervention rate was low, at 0.8%, so ipants did not experience any interventions. It is unclear what there was not much room for improvement from a safety per- factors contributed to the high rate of interventions for par- spective. It was therefore concluded that project resources ticipants who were blind at this location. There was a rela- would be better spent elsewhere. tively high proportion of yielding vehicles, and it may be that However, at this particular single-lane roundabout, partic- participants crossed in what they perceived as a gap but what ipants experienced relatively long pedestrian delay, probably was actually a yield that was not detected by the blind pedes- due to the very low yielding rate by drivers and the tendency trian. Individuals may have initiated crossing at the same time of participants to wait for long gaps before initiating cross- a yielded vehicle began to move. In this scenario, the O&M ing rather than forcing yields. The fact that interventions specialist would likely have intervened. Anecdotal observations were relatively low at the Charlotte location led the team to seem to support this conclusion. believe that acoustic conditions at this intersection facilitated At the Golden two-lane roundabout, the intervention rate the use of a gap detection strategy, that participants recog- dropped from 2.8% and 2.4% of trials prior to installation of nized this fact and used this strategy, and that the use of this treatments (for the raised crosswalk and the pedestrian hybrid strategy, while resulting in delay, yielded an acceptable level beacon, respectively) to zero after installation of treatments. of risk. It is concluded that a treatment is not necessary at this The RCW treatment reduced average pedestrian delay from roundabout under prevailing traffic conditions when crossed 17.0 s to 8.0 s. The PHB reduced delay from 16.0 s to 5.8 s on by blind pedestrians who report they cross streets independ- average for crossing two lanes of traffic. The team concludes ently. It is unclear if and how behavior and performance that without treatment in place, pedestrians who are blind measures at this site would change with higher traffic volumes and who cross the street are exposed to an unacceptable level and fewer (large) gaps. of risk. It is further concluded that the risk level appeared In regard to the Golden single-lane roundabout, there was acceptable after either of the tested treatments was installed not a statistically significant difference between the interven- at this site and under prevailing traffic conditions. It is unclear tion rate at pretest (1.4% of crossings) and posttest (0.5%). if and how crossing performance would change with higher Both studies further showed a relatively low average delay for traffic volumes or at a site with different geometry. participants of 11.9 s and 12.1 s, respectively. No treatment The team was surprised that the intervention rate for both was installed at the single-lane roundabout, and the same par- treatments was zero, as it was anticipated that the raised cross- ticipants participated in both rounds. The decision for two walk would not yield as great a risk reduction as the PHB. Field studies without treatment installation was motivated by the notes from a team observer indicate that there were eight risky goal to test for a learning effect in participants with repeated multiple threat crossings at the raised crosswalk that did not (twice) exposure to the same site and the same study protocol. actually result in interventions. No such events were recorded The same participants who crossed at this site also crossed at the PHB. Additional research at other locations and with at the studied two-lane roundabouts to allow for a direct other individuals is necessary to determine whether there is in within-participant comparison of a single-lane and a two-lane fact no difference in risk between these two treatments. roundabout. The fact that no learning effect was evident at To summarize, the key observations from the field studies the single-lane roundabout from a safety or delay perspective were: gives confidence that any pretestposttest difference at the two- lane roundabout can in fact be attributed to a treatment effect. That it is possible to apply the analysis framework to field The team concludes that the Golden single-lane roundabout studies and to describe pedestrian crossing performance did not pose extraordinary crossing challenges under prevail- in measurable terms consistent with the traffic engineer's